Development of “smart textiles” has been an active area of interest to improve various properties such as stain resistance, waterproofing, colorfastness and other characteristics achievable through advanced treatment using plasma technologies, microwave energy sources and in some cases, chemical treatments.
Atmospheric Plasma Treatment (APT) improves fiber surface properties such as hydrophilicity without affecting the bulk properties of these fibers, and can be used by textile manufacturers and converters to improve the surface properties of natural and synthetic fibers to improve adhesion, wettability, printability, dyeability, as well as to reduce material shrinkage.
Atmospheric-pressure plasma (or AP plasma or normal pressure plasma) is the name given to the special case of a plasma in which the pressure approximately matches that of the surrounding atmosphere. AP plasmas have prominent technical significance because in contrast with low-pressure plasma or high-pressure plasma no cost-intensive reaction vessel is needed to ensure the maintenance of a pressure level differing from atmospheric pressure. Also, in many cases these AP plasmas can be easily incorporated into the production line. Various forms of plasma excitation are possible, including AC (alternating current) excitation, DC (direct current) and low-frequency excitation, excitation by means of radio waves and microwave excitation. Only AP plasmas with AC excitation, however, have attained any noteworthy industrial significance.
Generally, AP plasmas are generated by AC excitation (corona discharge) and plasma jets. In the plasma jet, a pulsed electric arc is generated by means of high-voltage discharge (5-15 kV, 10-100 kHz) in the plasma jet. A process gas, such as oil-free compressed air flowing past this discharge section, is excited and converted to the plasma state. This plasma then passes through a jet head to arrive on the surface of the material to be treated. The jet head is at earth potential and in this way largely holds back potential-carrying parts of the plasma stream. In addition, the jet head determines the geometry of the emergent beam. A plurality of jet heads may be used to interact with a corresponding area of a substrate being treated. For example, sheet materials having treatment widths of several meters can be treated by a row of jets.
AP and vacuum plasma methods have been utilized to clean and activate surfaces of materials in preparation for bonding, printing, painting, polymerizing or other functional or decorative coatings. AP processing may be preferred over vacuum plasma for continuous processing of material. Another surface treatment method utilizes microwave energy to polymerize precursor coatings.